The invention relates to a method of knitting composite fibers, such as, for example, nylon, glass fiber, or graphite, into complex shapes, more particularly, complex tubular shapes in the form of matrices for impregnation with organic or inorganic plastics and other settable moldable substances, including glass, organic polymers, natural and synthetic rubbers and resins. I refer generically to all of these as a curable impregnate. The resulting product is a light-weight, high strength composite for industrial and like uses. I refer to the product as a matrix with cured impregnate. The invention also relates to an industrial method of making matrices of fittings and the like, including knitting tubular elements on a knitting machine and by knitting techniques, to construct various shapes including tubular "T" fittings, tubular "Y" fittings, hemispheric and cubic shapes, used as a ready-to-fit matrix which may then be stretched over a mandril in the shape in which it was knitted before plastic is applied to it to form the finished composite product. It is further contemplated that other complex shapes such as helmets, protective clothing for sports or bullet-proof clothing be made by my novel method. A preferred illustration is shown on a flatbed knitting machine.
One technique which is performed within the purview of the invention is the making of tubular "T" or similar complex shaped matrices on a knitting machine. In the instance of a tubular "T", the tubular top or cross of the "T" is knitted first and then, while the vertical tubular leg is being knitted, the machine continues to knit flat gussets on either side of the vertical leg in order to maintain a proper measure of tension on courses knitted across the horizontal width (length of horizontal tube) of the knitted piece.
In a tubular offset shape with, for example, two extensions offset along parallel axes with an intermediate connecting portion, flat gussets may be provided along the tubular portions to maintain linear tension along the courses of the knitted piece while flechages are knitted for the course or turn at the junctures of the extensions with the intermediate connecting portion. The flechage may be knitted by conventional knitting techniques. One such technique is that of knitting successively, partial courses of gradually increasing or decreasing length to form a turn in the tubular portions. This technique maintains substantially the same tension throughout the knitting process so that flat gussets may not be necessary in some offsets.
The invention further relates to a method of making a light-weight, high strength composite; e.g., a pipe fitting consisting of the steps of knitting a matrix into a formed selected tubular shape to define a knitted fabric matrix in the shape of the product to be manufactured, inserting a mandril coated, if needed, with a release agent and applying the plastic material to the formed knitted fabric matrix.
Other knitting techniques known to those in the knitting arts and compatible with the knitting of tubular complex shapes for the purposes of the invention are: intarsia--knitting separate fields to achieve non-rectangular construction: presser foot and stitch pressers, which allow the knitting of non-rectangular pieces; inlay--to increase the amount of knitted material within the matrix and to control lateral stretch; reinforcement and placement intarsia to spot knit additional material where extra strength may be required; and plating; i.e., the knitting of two different fibers at the same time in such a manner as to make one fiber more prominent on one face of a knitted product.
The invention also relates to the matrices produced by such techniques and to the products formed by such matrices when impregnated with plastic or other curable impregnate.